JPS6326139B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a colored polyester hollow molded article.

More specifically, the present invention relates to a hollow container made of thermoplastic polyester transparently colored with a specific pigment.

Thermoplastic polyesters, of which polyethylene terephthalate is a typical example, have traditionally been used for various containers, films, It is processed into sheets and used extensively as packaging materials.

With the advancement of blow molding technology, the use of hollow containers such as bottles and cans has been particularly remarkable in recent years, and they are now used as containers for foods, pharmaceuticals, cosmetics, etc.

Most of these hollow containers made of polyester are commercially available in an uncolored and transparent state. However, depending on the use of foods, medicines, cosmetics, etc., it is often necessary to add coloring to further improve performance such as light-shielding properties and decorative properties.

In the case of glass, which is widely used as a container material, the typical colored bottle is a brown bottle.

The first object of the present invention is to provide a hollow thermoplastic polyester container that is transparent or translucent and colored in a brownish color so that it has better light-shielding properties than conventional thermoplastic polyester hollow containers and allows the content of the filling to be seen from the outside like a glass bottle. The purpose is to obtain a hollow container.

A second purpose is to obtain a hollow colored polyester container in which when foods, medicines, cosmetics, etc. are filled and stored, the coloring agent of the container will not be leached into the filled material.

A commonly used method for coloring plastics is to melt and knead them using dyes, pigments, dispersants, etc. as appropriate.

However, the reality is that almost no technology has been established for colored transparent molded products of polyester containing ethylene terephthalate repeating units as a main component, particularly for colored transparent hollow molded products.

Usually, when the purpose is to obtain colored molded products with excellent transparency, dyes are used as coloring materials.

For example, they are called oil-soluble dyes, and there are various types of solvent yellow, solvent red, and solvent green listed in the color index. A dye is used. However, molded articles transparently colored with dyes have the disadvantage of color migration. In other words, when dye-colored molded products have a high temperature atmosphere, the dye tends to rise to the surface of the resin to be colored, and when they come into contact with water, alcohol, edible oils, etc., the dye from the colored molded product may dissolve into these solvents. It has a property (transitionality).

Considering that many foods, medicines, cosmetics, etc. use water, alcohol, and oil as their main solvents, the transferability of these colorants is a fatal drawback for colored containers used for foods, medicines, cosmetics, etc. Become.

In addition to dye-based colorants, pigment-based colorants are also widely used as plastic colorants, and molded articles colored with pigment-based colorants usually exhibit less migration than dye-based colorants.

However, several other problems arise with pigment-based colorants. That is, many pigment-based coloring materials are insoluble in polymer systems, and tend to become opaque or the pigments may aggregate, making it difficult to achieve uniform coloring.

In addition, the stretching tends to create voids and increases gas permeability, which also causes a decrease in the storage stability of the contents.

Furthermore, in the case of polyesters based on ethylene terephthalate repeating units, the use of pigment-based colorants presents very different technical problems than in the case of other plastics.

Polyester mainly composed of ethylene terephthalate repeating units has a tendency to crystallize itself, and when crystallization occurs, it becomes white and opaque. Therefore, molding conditions must be carefully selected to mold transparent hollow containers. For example, molten resin is cooled and solidified in a mold set at a temperature of 20 to 30° C. or less to prevent crystallization.

However, polyester, which is originally crystalline, increases the crystallization rate when it contains a substance that becomes a crystal nucleus, that is, a crystal nucleating agent. It is often impossible to prevent it.

There are numerous patents on nucleating agents for accelerating the crystallization rate of polyesters. Among these patents are patents that use pigments and dispersants for plastic coloring as nucleating agents. Examples include titanium oxide (white pigment) and carbon black (black pigment) found in Japanese Patent Publication No. 45-9740, and phthalocyanine pigments found in Japanese Patent Publication No. 46-15024.

Furthermore, it is reported in US Pat. No. 1,117,139 that a specific metal stearate, which is commonly used in conjunction with pigment-based coloring materials, also serves as a nucleating agent for polyester.

It is known that when polyester to which these nucleating agents are added is subjected to melt injection molding, it becomes a molded product with extremely advanced crystallization. Therefore, it is technically difficult to obtain transparent or semi-transparent hollow molded products by coloring polyester mainly composed of ethylene terephthalate repeating units with a pigment-based coloring material, as is the purpose of the present invention, which would be unimaginable with other resins. Accompany.

For this reason, until today, hollow containers made of colored polyester have been used as containers for foods, medicines, cosmetics, etc., and they have no tendency for colorants to migrate into the contents, and are transparent enough to allow the contents to be seen through. No excellent container had yet been found.

In view of the current situation, the present inventors have developed a number of dyes,
As a result of extensive research into pigments and dispersants, it was discovered that a brown-colored transparent hollow molded article suitable for the above purpose could be obtained.

That is, for 100 parts by weight of a thermoplastic polyester in which 80 mol% or more of the acid component is terephthalic acid, 80 mol% or more of the glycol component is ethylene glycol, and has an intrinsic viscosity of 0.6 to 2.0, (a) A colored polyester hollow molded body made by blending 0.001 to 2.0 parts by weight of iron oxide with an average particle diameter of 0.01 to 0.03μ, (b) 0.1 part by weight or less of carbon black, and (c) 0.001 to 0.4 parts by weight of magnesium stearate. It is.

The thermoplastic polyester having ethylene terephthalate as a main repeating unit as used in the present invention usually has an acid component of 80 mol% or more, preferably 90 mol% or more of terephthalic acid, and a glycol component of 80 mol%, preferably 90 mol%. % or more of polyester is ethylene glycol, and the remaining acid components include isophthalic acid, diphenyl ether,
4,4'-dicarboxylic acid, naphthalene 1,4- or 2,6-dicarboxylic acid, decane 1,10-dicarboxylic acid, adipic acid, sebacic acid, hexahydrophthalic acid, and as other glycol components propylene glycol, 1 , 4-butanediol, neopentyl glycol, diethylene glycol,
1,6-hexanediol, cyclohexanedimethanol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyethoxyphenyl)propane, or P-oxybenzoic acid as the oxyacid, It means a polyester copolymerized with P-oxyethoxybenzoic acid or the like.

Particularly preferred copolymerization components are isophthalic acid and/or neopentyl glycol. Alternatively, it may be a blend in which polyethylene terephthalate and copolymerized polyester are blended so that the content of ethylene terephthalate repeating units is 80 mol% or more of the total amount.

The thermoplastic polyester used in the present invention has an intrinsic viscosity of 0.6 to 2.0, preferably 0.7 to 1.5.
It is. Particularly preferred is polyester produced by melt polymerization, which is further heat-treated or solid-phase polymerized at a temperature of 180 to 250°C under high vacuum or in an inert gas atmosphere to reduce the oligomer (low molecular weight substance) and acetaldehyde content. It is made of polyester.

When the intrinsic viscosity is less than 0.6, the mechanical performance of the molded product is poor, and when it exceeds 2.0, melt molding becomes difficult and a hollow container with an excellent appearance cannot be obtained.

In addition, the intrinsic viscosity refers to the 30
This is the value of intrinsic viscosity measured at °C.

Further, iron oxide Fe ₂ O ₃ XH ₂ O of the present invention is represented by the general formula and has crystal water (X>
0) but does not contain water of crystallization (X=0)
However, the more preferable iron oxide temperature is 300℃.
The weight change rate is 8% or less when heat treated with.

The average particle size of iron oxide used in the present invention is 0.01 to 0.03μ.

If the average particle size exceeds 0.03μ, the polyethylene terephthalate molded product will lose its transparency, and
If it is less than 0.01μ, there will be difficulties in manufacturing technology and the dispersibility will be worse.

Furthermore, the blending ratio of iron oxide is 100% polyester.
It is 0.001 to 2.0 parts by weight per part by weight.

If it is less than 0.001 part by weight, there is almost no coloring effect;
If it exceeds 2.0 parts by weight, the transparency of the molded product will deteriorate and crystallization will occur, making it impossible to obtain a hollow container of the desired shape during blow molding.

The carbon black may be of channel type or furnace type, but channel type is more preferable.

The purpose of adding carbon black is to adjust the brightness of the brown color, and its amount is 0.1 parts by weight or less, preferably 0.001 to 0.05 parts by weight, per 100 parts by weight of polyester.

If it exceeds 0.1 part by weight, the polyester will crystallize during molding and a transparent hollow molded product will not be obtained.

Magnesium stearate used in the present invention is mainly blended to improve the dispersibility of pigments. The blending amount is per 100 parts by weight of polyester.
0.001 to 0.4 parts by weight of magnesium stearate. If the amount is less than 0.001 part by weight, it will not be effective in improving the dispersibility of iron oxide and carbon black, and if the amount exceeds the upper limit, the moldability of the blow molded product will deteriorate.

Until now, no research has been found on dispersants for transparently coloring polyester with pigment-based coloring materials, but the inventors have found that magnesium stearate is effective in improving the dispersibility of iron oxide and carbon black. It was found that it worked equally well.

Calcium stearate and sodium stearate, which are used in general plastics, speed up the crystallization rate of polyester and prevent the molded product from becoming transparent. Further, potassium stearate, lithium stearate, fatty acid ester, etc. cannot improve the dispersibility of iron oxide and carbon black in polyester.

It was a completely unexpected result that magnesium stearate improved the dispersibility of these pigments to the same extent as alkylene bis fatty acid amides without substantially altering the crystallization rate of the polyester.

The method for obtaining the colored hollow molded body of the present invention is to mix iron oxide, carbon black, magnesium stearate, and polyester in a desired concentration in a mixer such as a Henschel mixer, super mixer, or tumbler, then melt and knead in an extruder. A method is to make colored pellets by molding the pellets using a blow molding machine, or to mix high-concentration iron oxide, carbon black, magnesium stearate and polyester in the same manner as above, and after melt-kneading, to form high-concentration master pellets. There is a method in which the pellets are prepared, mixed and diluted with non-colored pellets to a desired concentration, and then molded using a blow molding machine.

It is also possible to dry blend the colorant composition with the desired concentration and polyester and mold it directly with a blow molding machine, and changes in application such as the blending order of each composition and the creation of master pellets for each single composition are subject to change. All are included in the invention.

Regarding molding with a blow molding machine, it can be carried out in the same way as blow molding of uncolored polyester. For example, after injection molding with extrusion blow molding (generally called direct blow molding) or injection blow molding (injection blow molding), compressed gas is applied to the parison (a cylindrical molded product with an open bottom that is the precursor of a hollow container) before it solidifies. A blow molding method or a method called biaxial stretch blowing is used to produce a parison with a bottomed opening by injection molding or extrusion molding, and then the parison is adjusted to an appropriate temperature for stretching, for example, 70 to 150°C, using a stretch blowing device. A blow molding method can be used in which axial stretching using a stretching rod and circumferential stretching using compressed gas are carried out simultaneously or sequentially.

It goes without saying that the colored hollow molded article of the present invention may be molded with addition of conventional additives such as an antistatic agent, an ultraviolet inhibitor, an antioxidant, and a mold release agent.

Furthermore, it may be a molded article that is blended with other thermoplastic resins within a range that does not impair transparency.

The colored hollow molded article of the present invention retains the excellent mechanical properties, gas barrier properties, chemical resistance, and aroma retention properties inherent to polyester, and although it is colored brown, it is difficult to see through the contents of the container. It has a glossy appearance and has the excellent property that almost no colorant is leached even when filled with water, alcohol, or oil, making it especially suitable for containers for foods, pharmaceuticals, cosmetics, etc. It is something.

Examples of the present invention will be described in detail below along with comparative examples.

In addition, parts in Examples and Comparative Examples mean parts by weight.

Example (1) Polyethylene terephthalate with an intrinsic viscosity of 0.81
100 parts, 1.0 part of iron oxide with an average particle size of 0.02μ, 0.04 part of carbon black with an average particle size of 15μμ, and 1.0 part of magnesium stearate were mixed in a tumbler for 10 minutes at room temperature, and then heated to the resin temperature in a 40mm diameter extruder.
Colored master pellets were produced after melt-kneading at a temperature of 280°C.

Next, 10 parts of this colored master pellet and 90 parts of the above-mentioned polyethylene terephthalate having an intrinsic viscosity of 0.81 were placed in a rotary dryer at 160°C to a thickness of 0.1 mm.
After stirring and drying under reduced pressure of Hg for 4 hours,
Using a −95 injection molding machine, the cylinder temperature was set at 260℃, 280℃, and 290℃ from the hopper side, the injection pressure was 40Kg/cm ² in gauge pressure, the mold temperature was 20℃, and the injection and cooling cycle time was A bottomed parison with an opening at the top was molded under molding conditions of 15 seconds and 25 seconds.

The parison had an outer diameter of 30 mm, an inner diameter of 24 mm, a length of 140 mm, and an average wall thickness of 3 mm, but no whitening due to crystallization of polyethylene terephthalate was observed in the parison, and it had a dark brown color.

Next, the colored parison was transferred to a biaxial stretching blow molding machine, heated with a parison heating device until the surface temperature of the parison reached 115°C, and then
A beer bottle-type biaxially stretched bottle with a total length of 265 mm, a body outer diameter of 80 mm, and an internal volume of 1000 ^{ml was obtained under the stretching blowing conditions of 80 Kg/cm 2 ,} compressed gas pressure of 18 Kg/cm 2 , and blow mold temperature of 20°C.

The body of this bottle had been stretched to an average wall thickness of 400 μm, had no pigment agglomeration, was uniformly colored, and had an appearance with excellent transparency and gloss.

The two brown colored bolts obtained in this way
Fill 950ml each of 50% by weight ethyl alcohol aqueous solution and edible oil, and after sealing, store in an atmosphere of 40℃.
A storage test was conducted for 50 days.

After 50 days, the 50% ethyl alcohol aqueous solution and edible oil that had been filled were taken out and the color of each solution was examined, but no coloration was observed. Further, the spectrum of this solution was determined using a photoelectric colorimeter (Hitachi 124 Spectrophotometer) at a wavelength of 200 mμ to 800 mμ, but no absorption due to the colorant was observed.

Example 2 Polyethylene terephthalate with an intrinsic viscosity of 1.20
100 parts, 0.6 parts of iron oxide with an average particle size of 0.01μ, 0.05 parts of carbon black with an average particle size of 15μμ, and 0.6 parts of magnesium stearate were mixed in a V-type blender for 15 minutes at room temperature, and then dried at 170℃ for 4 hours to form a 40mm
Resin temperature is 285℃ in extruder with screw diameter
After melt-kneading, master pellets were produced.

Next, 20 parts of this master pellet and the intrinsic viscosity
1.20 with 80 parts of the above polyethylene terephthalate in a tumbler for 10 minutes, dried in a hot air dryer with a dehumidifier at 180°C for 3 hours, and then used an extrusion blow molding machine manufactured by Japan Steel Works (Nippon Koutex V/8). Extrusion blow molding was carried out by setting the cylinder temperature and die temperature to 270 to 290°C, the compressed gas pressure to 4 kg/cm ² , and the temperature of a blow mold having a cavity shaped like a small beer bottle with a volume of 500 ml to 20°C.

The obtained molded product is shaped according to the mold shape and the volume is
It was a 500 ml transparent, uniformly colored brownish-brown bottle.

The average thickness of the body of this bottle is 500μ, and when looking at the ultraviolet and visible spectra of this part, ultraviolet rays below 370μ are almost completely blocked;
It was found that visible light with longer wavelengths can be transmitted well.

It is well known that most of the photodeterioration of foods, medicines, and cosmetics is caused by ultraviolet rays, but the hollow container obtained by the present invention has the ability to see through the contents from the outside and to block only the ultraviolet rays to protect the contents. It has an excellent ability to protect food, medicines, cosmetics, etc., making it ideal for containers. For comparison, the ultraviolet and visible spectra of the 500μ thick body were also taken for an uncolored transparent hollow container molded under the same conditions as this example using only polyethylene terephthalate with an intrinsic viscosity of 1.20 without using any colorant composition. , 310 mμ for uncolored containers
Although it blocked the following ultraviolet rays, more than 85% of ultraviolet rays with longer wavelengths of 310 to 370 mμ were transmitted.

Comparative example (1) Comparatively (1), the amount of carbon black was 1.20
Colored master pellets were prepared in the same manner as in Example (1) except that the pellets were diluted with uncolored pellets, and then parisons were molded using an injection molding machine.

The parison obtained here had a dark brown color, and at the same time, the central layer in the thickness direction of the parison had a slightly whitish dark brown color. This is thought to be due to the crystallization of the central layer of the parison.

Next, the parison was subjected to stretch blow molding under the same conditions as in Example (1), but since the parison had already crystallized, it could not be shaped according to the cavity of the blow mold, resulting in a distorted hollow of about 200 to 300 ml. All it took was a container.

In addition, this distorted-shaped bottle was opaque no matter where you looked at it.

This is because 0.12 parts of carbon black was added during parison molding, and crystallization of the polyester progressed significantly.

The amount of carbon black added is 0.1 as in the present invention.
It is necessary to make it less than 100%.

Comparative Example (2) The molding of the final bottle was carried out in the same manner as in Example (1) except that magnesium stearate was not blended in Example (1).

The appearance of the resulting bottle was poor in dispersibility of iron trioxide and carbon black, and uneven coloring was observed, so it had little commercial value.

Comparative Examples (3) and (4) Example (1) except that instead of magnesium stearate, calcium stearate was added as Comparative Example (3) and sodium stearate was added as Comparative Example (4). Master pellets were prepared and parisons were formed in exactly the same manner as in 1).
The central layer in the thickness direction of each of the obtained parisons was crystallized and turned whitish and dark brown. Subsequently, the parison was subjected to stretch blow molding under the same conditions as in Example (1), but it was not possible to shape the parison according to the cavity of the blow mold, and only a distorted hollow container of about 300 to 700 ml was obtained.

Claims (1)

[Scope of Claims] 1. 100 parts by weight of a thermoplastic polyester in which 80 mol% or more of the acid component is terephthalic acid, 80 mol% or more of the glycol component is ethylene glycol, and has an intrinsic viscosity of 0.6 to 2.0. On the other hand, (a) 0.001 to 2.0 parts by weight of iron oxide having an average particle diameter of 0.01 to 0.03μ, (b) 0.1 part by weight or less of carbon black, and (c) 0.001 to 0.4 parts by weight of magnesium stearate are blended. Colored polyester hollow molded body.